Block boot for railway track systems

ABSTRACT

A block boot (1) that has a rectangular ground plan, a bottom (5), and four side walls (2, 3). On the interior of the side walls (2, 3), ribs (10, 15) extending in parallel to the bottom are arranged. At least one of these ribs (10, 15) tapers from the respective side wall (2, 3) toward the interior of the block boot to a free end having a vertex line (24, 25). This block boot is simple to manufacture and offers improved properties with regard to static and dynamic rigidity in operation.

The invention relates to a block boot for railway track systems according to the preamble of claim 1.

So-called slab tracks are increasingly preferred to ballasted tracks since they allow an increased performance of the track with regard to the attainable speeds and reduced maintenance costs. In such slab tracks, sleeper block units are used where a sleeper block that is usually made of concrete is received in a block boot made of molded rubber and an elastomer damper is placed between the bottom of the sleeper block and the bottom of the block boot. The block boot is encased in concrete, and on the upper side of the sleeper block, a fastening system for a rail is arranged. It has been known for some time to provide ribs on the inner walls of such block boots in order to reduce the contact area between the block boot and the sleeper block.

In patent DE 101 96 374 B4 it is explained that in such sleeper block units the dynamic to static rigidity ratio increases with the vertical movement of the block and therefore the deformation of the elastomer pad under dynamic loads is impeded by an contact area between the block and the inner wall of the block boot, and that this relationship is a phenomenon known as the wedge effect. The cited patent then describes a solution for eliminating the wedge effect without reducing the lateral resistance of the track and for decreasing the dynamic to static rigidity ratio. According to this solution, the ribs of the block boot are provided with fins which extend from the ribs inward. The fins ensure a minimum contact area between the sleeper block and the ribs in the sleeper boot while the sleeper block unit is being encased. Once the fins have been crushed or abraded by the sleeper block in operation, the wedge effect is largely eliminated and the free vertical movement of the sleeper block and the full intended deformation of the elastomer pad under dynamic loads is enabled within a predetermined range.

However, the fins lead to some difficulties in the manufacture of the block boot. Thus, the mold has to be thoroughly cleaned before every molding process. In particular, the fine grooves that will subsequently form the fins have to be carefully cleaned so that they will be entirely filled with rubber during the molding process. As the finished block boot is removed from the mold, there is a risk that the fine fins remain caught in the aforementioned grooves and are torn off from the block boot. Finally, the risk that the fine fins are already snapped or sheared off while the block boot is assembled with the sleeper block cannot be entirely excluded either.

On the background of this prior art, it is the object of the invention to provide a block boot in the manufacture of which the aforementioned difficulties do not arise and which moreover offers improved properties in operation.

According to the invention, this object is achieved by the features indicated in the characterizing part of claim 1. In the present context, the term “vertex line” designates a theoretical line extending furthest from the respective side wall along the rib at the free end of each rib.

The tapered shape of the rib eliminates a weakness of the known prior art, namely the small cross-sectional area of the fin at its junction to the rib, and thereby promotes both a simpler manufacture of the block boot and its durability without impairing its advantageous properties.

Due to the small contact area in the area of the vertex line of the ribs between the latter and the subsequently inserted sleeper block, the friction between the sleeper block and the block boot as it is deflected under a load is reduced and thus the rigidity of the sleeper block unit is somewhat reduced. Simultaneously, this reduction in rigidity facilitates a higher deflection of the rails under vertical loads applied by rail vehicles.

Particular embodiments of the invention are defined in the dependent patent claims.

Exemplary embodiments of the invention will be described hereinafter with reference to the appended drawings showing

FIG. 1 a top view of a block boot of the invention;

FIG. 2 a section along line II-II in FIG. 1 through a long side wall of the block boot of FIG. 1 ;

FIG. 3 a detail of FIG. 2 on an enlarged scale over FIG. 2 ;

FIG. 4 a section along line IV-IV in FIG. 1 through a short side wall of the block boot of FIG. 1 ; and

FIG. 5 a detail of FIG. 4 on an enlarged scale over FIG. 4 .

Block boot 1 according to FIG. 1 has a substantially rectangular ground plan with rounded edges 4, two long side walls 2, two short side walls 3, a bottom 5 (FIG. 2 ) and an upper opening 6 with a surrounding rim 7. Its height is e.g. 158 mm. As known from the prior art, side walls 2 and 3 are slightly inclined in order to allow a later replacement of the sleeper block and of the encased block boot 1.

FIG. 2 shows a section through long side wall 2 of block boot 1 along line II — II in FIG. 1 . Rim 7 of upper opening 6 upwardly tapers to an apex 8 that will subsequently lie against the sleeper block, prevents the ingress of dust and guides water running down on the outside of the sleeper block to the outside of block boot 1. Externally, rim 7 is provided with a surrounding bulge 9 that reinforces rim 7 and forms a mark for the concrete filling height while the sleeper block unit is being encased. The transition from side wall 2 as well as side wall 3 (FIG. 4 ) to bottom 5 forms a radius. On the inside of side wall 2, ribs 10 that extend in parallel to bottom 5 and rim 7 are arranged, in the illustrated example 18 of them. Alternatively, more or less ribs 10 may be provided. In the illustrated example, the dimensions of ribs 10 and their intervals are uniform.

FIG. 3 shows a detail of FIG. 2 illustrating two ribs 10 at an enlarged scale over that of FIG. 2 . As shown, seen in cross-section, each one of ribs 10 first tapers slightly conically from a base width 13 toward the interior of block boot 1 and ends in a rounded shape having a radius 11. Reference numeral 24 denotes a vertex line that extends at the highest point of rib 10, as measured from side wall 2, along rib 10 perpendicularly to the drawing plane of FIG. 3 . 12 denotes the height of rib 10, and 14 the space between two ribs 10. Due to the radius 11 of ribs 10, the contact area between the block boot and a sleeper block subsequently received therein is nearly reduced to a contact line per rib 10 in the area of vertex line 24.

FIG. 4 shows a section through short side wall 3 of block boot 1 along line IV-IV in FIG. 1 . On the inside of side wall 3, ribs 15 that extend in parallel to rim 7 and bottom 5 are arranged, in the illustrated example 9 of them. Alternatively, more or less ribs 15 may be provided. In the illustrated example, the dimensions of ribs 10 and their intervals are uniform. In side wall 3, directly above the bottom, a drainage opening 23 is provided so that water that may be present in block boot 1 may flow off before encasing.

FIG. 5 shows a detail of FIG. 4 illustrating one rib 15 entirely and a second one partly at an enlarged scale over that of FIG. 4 . As shown, each one of ribs 15 extends toward the interior of block boot 1 and asymmetrically tapers from a base width 19 to an apex having a small radius 17 of e.g. less than 1 mm, while a shorter wall section 20 forms a steeper angle and a longer wall section 21 forms a flatter angle with side wall 3. Wall sections 20 and 21 are preferably straight but may alternatively be slightly convex. Reference numeral 25 denotes a vertex line that extends at the highest point of rib 15, as measured from side wall 3, along rib 15 perpendicularly to the drawing plane of FIG. 5 . 18 denotes the height of rib 10, and 22 the space between two ribs 15. Due to the radius 17 of ribs 15, the contact area between the block boot and a sleeper block subsequently received therein is nearly reduced to a contact line per rib 15 in the area of vertex line 25. At the end of longer wall section 21 near the wall, a radius 16 may be provided.

Due to this design of ribs 15, the rigidity of the block boot under lateral forces is variable. The higher the lateral force, the larger the contact area becomes since rib 15 is increasingly compressed and the resistance to the lateral forces increases. Furthermore, the described design of the ribs enhances the elastic properties of the block boot in the sense that the block boot recovers its original shape more quickly under low lateral forces. Simultaneously, the variability of the contact surfaces under lateral forces also increases the longevity of the block boot since a constant contact of the entire surface of the rib on the sleeper block is avoided.

LIST OF REFERENCE NUMERALS

-   -   1 block boot     -   2 long side wall     -   3 short side wall     -   4 edge     -   5 bottom     -   6 upper opening     -   7 rim     -   8 apex     -   9 bulge     -   10 rib, long side     -   11 radius     -   12 height     -   13 base width     -   14 space     -   15 rib, short side     -   16 radius     -   17 radius     -   18 height     -   19 base width     -   20 wall section     -   21 wall section     -   22 space     -   23 drainage opening     -   24 vertex line     -   25 vertex line 

1. A block boot for railway track systems, intended to receive a sleeper block, the block boot having a rectangular ground plan with a bottom and four side walls, and ribs that extend in parallel to the bottom being arranged on the inside of the side walls, wherein at least one of the ribs tapers from the respective side wall toward the interior of the block boot to a free end having a single vertex line.
 2. The block boot according to claim 1, wherein seen in cross-section, the free end of the rib is approximately semicircular.
 3. The block boot according to claim 1, wherein seen in cross-section, the free end of the rib is approximately triangular.
 4. The block boot according to claim 3, wherein the triangular shape comprises a shorter flank and a longer flank.
 5. The block boot according to claim 2, wherein the rib is arranged on the longer side wall.
 6. The block boot according to claim 3, wherein the rib is arranged on the shorter side wall.
 7. The block boot according to claim 1, wherein a plurality of parallelly extending ribs are designed identically.
 8. The block boot according to claim 7, wherein the ribs are equally spaced.
 9. The block boot according to claim 1, wherein at their upper ends, the side walls have a surrounding rim which, seen in cross-section, ends in an upper apex.
 10. The block boot according to claim 1, wherein in at least one of the side walls, a drainage opening is arranged directly above the bottom.
 11. The block boot according to claim 4, wherein the rib is arranged on the shorter side wall. 